Saturday, September21, 2019

Sailing To Windward


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                                         Sailing to Windward
                                              "You must know yourself and your boat"
                                                          By Arvel Gentry
                                                     SAIL Magazine, January 1974
    Sailing a boat to windward requires, above all else,
concentration. And this concentration, by the best
helmsman, is more intense than a beginner can even hope
to comprehend. A great helmsman can "feel" the boat. And
he reacts instinctively with the proper twitch of the wheel
                                                                                                              December 1999
or tiller, always keeping the boat "in the groove" and
moving at its best. But what can you do to improve your
windward steering?
    First, you must know your boat. How does the boat
react to varying wind and sea conditions? Is it sluggish and
slow to respond, or is it quick to accelerate? How does this
responsiveness change with wind speed? Does the boat
tend to pound in short chop or does it cut right through it?
Can the tiller be moved quickly in choppy conditions                             Figure 1. Mainsail and genoa set up for
without slowing the boat, or must you move the helm                                        telltales and tufts.
slowly? How does boatspeed change with varying wind
    The first task when steering to windward is to keep the
sails at the proper angle to the wind; and a helmsman
usually has two visual clues to help him. If he sails too close
on the wind, his sails will luff. If he sails too far off, the sails
will stall. A stall usually is detected by watching yarn or
ribbon telltales placed about one foot behind the genoa
luff. When the lee telltale twirls, the sail is stalled.
    While both conditions, the luff and the stall, cause a
reduction in the driving force out of the sails, there are
usually several degrees of heading angle between the two
conditions. If the helmsman wanders back and forth                        Figure 2. Close-up of tuft system. Genoa luff is to right.
between the two extremes, he soon will be left far behind
the other boats. Even if he always sails right on the edge of          short tufts placed end to end with the first one right up
the luffing condition his boat performance still will be bad.          against the luff rope. (The aerodynamic principles behind
The boat may hit a wave or some chop. Then, after it has               this tuft system were described in the May and November
slowed, it will be too slow in accelerating back up to speed.          issues of SAIL.)
    A good helmsman must know when it is best to let the                   This tuft system (Figure 2) is based on the fact that the
sails luff momentarily or when to bear off slightly for quick          lee-side flow will separate in the form of a small bubble
acceleration. He must know just where between these two                right at the luff of a sail when the boat is headed slightly
conditions he will get the best steady state of windward               below the luffing condition. Behind this bubble, flow
performance. And equally important, he must know how                   remains attached and the sail is not stalled. The row of
to change his steering techniques with differing speeds                short tufts simply shows the size of the bubble (Figure 3).
and sea conditions.                                                    Please note that these drawings only show the first 18" of
    A good helmsman always knows how close he is to                    the genoa, and the sail angle difference in the drawings is
luffing or stalling, and how rapidly he is approaching one             exaggerated to illustrate the effects of the bubble.
of these conditions. While this does come with much                        When the sail is precisely on the verge of luffing, the
practice and experience, I've developed a special tuft                 stagnation streamline (the streamline that divides the
system that replaces the conventional single luff telltale to          windward and the lee-side air streams) curves right into
help shortcut this learning process.                                   the luff rope, and the lee-side separation bubble does not
    On my boat, the crew uses a complete set of telltales on           exist. All the leeside tufts, even the one right on the luff
both the genoa and the mainsail to achieve total sail trim.            rope, will lie down smoothly (Figure 3A). The windward
But the helmsman steers watching only the tuft system                  side frequently will be separated but this is not so
shown in Figure 1 .This system consists of a line of four              important as the tuft activity, or lack of it, on the lee side.
    As the boat heads off a bit, the stagnation streamline
moves slightly around to the windward side of the luff
rope. This causes high, leading edge velocities and low
pressures as the air makes the sharp turn around the luff.
After the air gets around to the lee side, it immediately
starts to slow down and its pressure starts increasing. The
boundary layer does not like this increase in pressure, and
it separates. If the turn around the leading edge has not
been too sharp, the flow soon will reattach itself to the sail
and continue aft to the leech (Figure 3-B).
    The farther off the wind the boat is heading, the larger
the separation bubble gets. Finally it bursts and the entire
lee side of the sail separates and the sail becomes stalled
(Figures 3-C and D). The number of twirling tufts tells you
the size of the bubble. They also tell you how close you are
to the luffing condition (no bubble at all), and how close
you are to the stall point. By watching the changes in the
tufts you also can tell how rapidly you may be moving
toward one of these unwanted conditions.
    When you first start sailing with this tuft system, don't
try to use it to steer the boat. Sail the boat as you usually do,
and then after you think you have the boat in the groove,
see just what the lee-side tufts are doing. Are they all lying
down smoothly, or is the first one slightly agitated? The
reaction of the tufts to different conditions does vary
slightly with different boats or sails, so I'll just show how
they work on my own boat.
                                                                                            Figure 3. Tuft system stages.
    On my genoa, the three tufts can twirl before the sail
stalls completely. In medium winds, the best windward                     without slowing the boat, and this maneuver actually
performance occurs when only the first lee tuft is slightly               helps you get to windward.
agitated.                                                                     If you see a smooth spot of water just ahead of a wave,
    In heavier air, over 15 knots, the genoa is kept on the               you might bear off slightly to gain extra speed just before
verge of luffing a good deal of the time and all the lee-side             you head up sharply to slice through the water.
tufts are lying down.                                                         Steering through waves and chop is complicated by the
    When boatspeed is lost because of wave action or lack                 pitching motion of the boat. This gets particularly bad
of concentration, head the boat off slightly until the first              when the wind begins to drop off, leaving behind a sloppy
two tufts twirl. Quickly glance at the knotmeter and as                   sea. Here you must search for the best compromise
soon as speed is back up, bring the boat back onto the wind               between having the genoa luff (or float) as the bow goes
until the tufts either lie down again, or the first one is                down, and having the sail stall when the bow comes back
slightly agitated.                                                        up.
    The basic concept in high winds is to keep the boat                       You should try to avoid being too far off the wind for
upright and to control exactly how the bow strikes each                   you will find that if you are, you will spend too much time
wave or chop. By watching the wave and chop patterns                      with the sails stalled. In other words, if necessary, let the
you will start to see situations where the proper changes in              sail luff briefly. Then when the pitching stops, bear off
the boat's heading will improve windward performance.                     slightly to accelerate back up to top speed.
    There are several ways to handle waves and chop. At                       In moderate winds and smooth water most steering
times you may have to bring the bow up to meet a short                    problems involve finding the angle that is the best trade-
wave that might stop the boat. The sail may luff                          off between boatspeed and pointing ability. This,
momentarily and the speed might drop slightly. You then                   incidentally, is where the tuft system works best. Once you
must head the boat off to accelerate back up to speed.                    find out just how much agitation (if any) should show on
Watch the tufts when you do this so you don't stall the sail.             the first lee side tuft to get the boat in the groove, it should
Also keep an eye on the next wave so that it doesn't hit you              be a simple matter to keep it there.
while you are heading too far off the wind. In fact, it might                 Remember though, that pointing ability is determined
be necessary to stay high for a second short wave before                  by the actual path of the boat through the water and not
you bear off to accelerate.                                               the angle of the boat relative to other boats around. If you
    Often you will find that only small changes in the bow                pinch too close to the wind you may seem to be pointing
position allow you to pass over the edge of a new wave                    high, but slower speeds and excessive leeway may
produce poor windward performance.                                          Of course you must remember that good boatspeed is
     Beating in light air presents a whole new set of                   never going to be much help if you are not sailing in the
problems, and concentration and a light tiller touch both               right direction. The helmsman always must keep his brain
are essential. Avoid rapid tiller movements, for this creates           in gear and constantly at work on developing situations.
both increased rudder drag and higher hull drag; the boat                   Better yet, he should have someone else worry about
now is being rotated by the rudder. When possible, let the              the tactics. That way he can concentrate only on how to
boat do the work for you.                                               steer to make the boat go fast.
     For example, if the wind shifts and the first two or three
lee-side tufts twirl, don't head the boat up by pushing the
tiller over. Instead, gently release the finger pressure that
has been holding back the slight weather helm, and let the
boat head up by itself. Then when the lee side tufts start to
lie back down, gently restrain the tiller again to stop the
boat's rotation.
     If weather helm is not enough to do this and you must
move the tiller yourself to get the right angle to the wind,
then do it smoothly and gently and give the boat plenty of
time to respond. Be patient.
     Good windward performance, of course, depends on
more than just the helmsman. The crew can help too. If it is
at all possible, the genoa should never be cleated on a
windward leg. A crew member should be on the winch at
all times watching the sail distance off the spreader, the
knotmeter, and the apparent wind speed indicator.
     If he sees the boat is losing speed because of chop, he
should let the genoa out so that it is several more inches off
the spreader. As boat speed comes back up, he should
bring the sail back in again. If the wind drops again, the sail
should go back out. If the sea gets smooth and the
helmsman starts to point up to take advantage of it, then
the genoa should come in.
     In some cases, this constant in-and-out genoa
adjustment is best accomplished with the barber haul
instead of the genoa sheet. In other cases the two should be
moved together It even may help to move the main
traveler or mainsheet to coincide with genoa movements.
All these sail adjustments should be made smoothly and
none should interfere with or counteract the actions of the
     It does help, when first practicing, to have the
helmsman and sheet tender constantly talk to each other.
But after a while, each one should be able to anticipate the
actions of the other without any verbal communication.
     Throughout all these maneuvers, the helmsman can
use the lee-side tufts to tell just where he lies between the
luffing and the stalled condition, and how rapidly he may
be changing from one phase to another. However, for top
performance, he should keep an eye on the tufts, on the
water just ahead of the boat, and on the knotmeter.
     Never look only at the tufts. Keep looking around so
you can learn to anticipate what oncoming waves or chop
will do to the boat. And curiously enough, the sensitivity of
this tuft system actually may give you more time to spend
looking forward and around rather than just staring at the
sail luff all the time. However, even with this new sailing
aid, long hours of practice and great concentration still are
the keys to good windward sailing.

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